Field
The present invention relates to a control device of a vehicle that estimates the slope of a road surface on which the vehicle travels on the basis of the vehicle speed, the rotation speed of a drive source, an acceleration operation amount, and so forth and controls an automatic transmission on the basis of the estimated slope.
Description of the Related Art
In Patent Document 1 (Japanese Patent Laid-Open No. 2010-151154), the following technique is disclosed. The slope of a road surface on which a vehicle travels is estimated on the basis of the vehicle speed, the engine rotation speed, an acceleration operation amount to the vehicle, and so forth. In the brake-on state (when a brake is operated), it is determined that the vehicle is traveling on a downhill, and hill descent control is carried out.
According to Patent Document 1, in the case of the brake-off state (when a brake is not being operated), the hill descent control is not carried out because the driver is not intending to decelerate the vehicle.
However, when the driver operates a brake detector such as a brake switch, a brake lever, or a brake pedal to carry out brake operation with the intention to decelerate the vehicle, if this brake detector is in failure, an ECU determines that the driver does not have the intention to decelerate the vehicle because a brake-on signal is not input from the brake detector. As a result, the ECU does not carry out the hill descent control even when the vehicle is traveling on a downhill.
Specifically, in the case in which power of an engine as a drive source is transmitted to a drive wheel via an automatic transmission, when the vehicle speed decelerates, the ECU determines whether the deceleration is caused by brake operation by the driver or by traveling of the vehicle on a flat road or an uphill. However, as described above, if the brake detector is in failure, even when the driver carries out brake operation with the intention to decelerate the vehicle while the vehicle is traveling on a downhill, the brake-on signal is not input from the brake detector to the ECU and thus there is a possibility that the ECU erroneously determines that the vehicle is traveling on a flat road or an uphill.
It will also be possible to equip the vehicle with an angle sensor or an inclination sensor and sense an uphill, a flat road, or a downhill in order to prevent the erroneous determination. However, providing the angle sensor or the inclination sensor requires high cost. To prevent the erroneous determination without high cost, a method of estimating an uphill, a flat road, or a downhill by using detection results of various kinds of detecting units with which the vehicle is equipped needs to be established.